Kaolin, also widely known as China Clay, gets its name from Gaoling Village near Jingdezhen, Jiangxi Province of China. Local miners discovered this white clay centuries ago and used it to manufacture fine porcelain, and the name “kaolin” has spread worldwide ever since. The main mineral component of kaolin is kaolinite, a hydrated aluminosilicate mineral with the chemical formula Al₂Si₂O₅(OH)₄. It belongs to 1:1 layered phyllosilicate. Pure kaolin is white or off-white. When mixed with iron oxide and other impurities, it may show light yellow, light red or gray tones. It feels soft and fine, with Mohs hardness of 1 to 2.5, low abrasion and stable chemical inertness, which makes it a precious non-metallic mineral resource with thousands of years of application history.
Kaolin forms over millions of years through natural weathering or hydrothermal alteration of parent rocks such as granite rich in feldspar. Under warm and humid climate conditions, rainwater continuously leaches the parent rock, dissolving soluble elements like potassium, sodium and calcium. The remaining silicon and aluminum components gradually recombine to form kaolinite crystals. There are three major deposit types: weathering residual type, sedimentary type and hydrothermal alteration type. China has abundant kaolin reserves, distributed in Guangdong, Jiangxi, Fujian, Shanxi and other regions. Global major producing areas include the United States, Brazil, the United Kingdom and France. Different deposit types bring raw kaolin with distinct particle size, purity and plasticity, determining different downstream application directions.
Plasticity is one of the most iconic features of kaolin. After mixing with proper water, kaolin can be shaped freely and maintain its form after drying, which is the fundamental reason why it became the core raw material for porcelain. Kaolin has high refractoriness, melting at around 1785℃, so it can be used for refractory products. Its fine lamellar particles provide good covering power, dispersibility and ink absorption capacity. Chemically, kaolin is inert and does not easily react with most acids and alkalis. It also has excellent electrical insulation performance. These comprehensive properties can be further optimized by purification, grinding, calcination and surface modification to meet diverse industrial requirements.
Ceramics is the most traditional application field. Kaolin serves as the main raw material for porcelain, sanitary ware, ceramic tiles and refractory ceramics. It improves the green body strength and whiteness after firing. The paper industry is the largest consumption field. Kaolin is used as coating and filler for paper. It fills gaps between plant fibers, smooths paper surface, improves glossiness and printability. In coatings and paints, kaolin acts as functional filler to enhance covering performance, reduce raw material cost and improve coating stability. In fiber glass, rubber and plastic industries, modified kaolin can reinforce the base material, improve dimensional stability and anti-aging performance. In environmental protection, kaolin with modified surface has strong adsorption capacity, which can be applied in waste gas and wastewater treatment.
Raw kaolin mined from mines contains quartz, mica and other impurities. The processing flow includes crushing, wet beneficiation, sedimentation, filtration, drying and ultra-fine grinding. High-end products require calcination and surface modification to adjust particle morphology and surface activity. With the continuous upgrading of manufacturing industry, market demand for ultra-fine, high-purity and functional kaolin keeps growing. The industry is paying more attention to green mining and comprehensive utilization of associated resources. Researchers are exploring new applications of kaolin in new composite materials and catalyst carriers, unlocking greater value of this ancient mineral material.
